A method for defect investigation of a component is described in which one surface of the component is obliquely ensonified through a liquid or gaseous first medium with a checking sound beam produced by a transmission/reception transducer. The method is performed by a system for defect investigation of a component that includes a transmission/reception transducer which produces a checking sound beam and is designed to obliquely ensonify one surface of the component through a liquid or gaseous first medium with the checking sound beam, and to receive a response sound beam which is reflected back from the surface to the transmission/reception transducer.
Methods and systems such as these for defect investigation of a component, in particular for ultrasound testing, are known in a wide range of embodiments. In order to allow defects close to a surface to be identified, the sound is injected obliquely, so that the injection direction differs from the normal to the surface of the component to be investigated. Water is normally, but not exclusively, used as the first medium. This immersion technique results in very good coupling between the checking sound beam and the component to be investigated. Furthermore, there is no direct contact between the component and the transmission/reception transducer, so that the surface of the component is not mechanically loaded.
However, it is initially not known when the checking sound beam will strike the surface and the actual recording of the component will thus start. The transmission/reception transducer is therefore placed—provided that the surface contour allows this—at an exactly adjusted distance from the component, or is readjusted during operation corresponding to the surface contour as determined in advance, in order to keep the distance from the component approximately constant. Furthermore, it is possible to determine the distance to the component using a separate measurement device element. This last variant is described, for example, in DE 42 23 502 A1. In addition to the obliquely injecting transmission/reception transducer, an additional, vertically injecting, transmission/reception transducer is provided. All three variants are, however, associated with considerable implementation complexity.